Tubular rudder with relief means



Dec..24, 1963 R. w. ERLBACHER 3,115,112

TUBULAR RUDDER WITH RELIEF MEANS Filed May 4, '1961 m x EM-ro E: ROBERTw. Em. BHCHER,

United States Patent "ice 3,115,112 TUBULAR RUDDER WITH RELEF MEANSRobert W. Erlbacher, 920 N. Fountain, Cape Girardeau, Mo. Filed May 4,1961, Ser. No. 107,671 14 Claims. (Cl. 114-166) This invention relatesto improvements in tubular rudders and in particular is concerned withtubular rudders having relief means for accommodating propeller races ofdifferent sizes which may vary with the load and speed of the vessel.

In the Kort rudder a tubular shell is used to enclose the propeller, asis well known in the art, while in the Erlbacher Patent No. 2,803,211, atubular shell is used spaced axially from the propeller to provide forincreased propulsion and steering efiiciency. In the Erlbacher patentdesign, the rudder may be used aft of the propeller in conventionalfashion or it may be used as a backing rudder in which case it is spacedslightly forward of the proeller.

p It has been recognized that as the revolutions per minute of thepropeller increase the diameter of the wheel race also generallydecreases. Since the tubular rudder designs are comprised of a tube offixed diameter, no allowance is made for this variation. As a result athigh r.p.m., when the propeller race is of a decreased diameter, andwhen more water is pushed through the rudder at high velocity, thetubular rudder is larger than necessary. It will be understood that theterm propeller race means the high velocity propulsion slip stream ofwater created by the turning of the propeller. When the vessel isoperating at top r.p.m. with increased loads there will be greaterslippage than when there is a light load at the same r.p.m. and thepropeller race is larger. Since the rudder is normally designed for anaverage r.p.m. and load, the variation in propeller race, size, andpassage of water through the tubular rudder, does not permit optimumoperating efficiency at other speeds and loads and losses in eificiencyand steering result.

By means of this invention there has been provided a tubular rudder foruse according to the Kort type of rudder and also the Erlbacher patenttype of rudder. This rudder has relief means and permits the rudder toaccommodate wheel races of increased diameter and permits increase offlow through the rudder at increased speeds and loads. The relief meanscan take the place of an enlarged or expandable internal rudderdimension as in the form of a rigid tubular rudder having a slottedsection closed by a rubber diaphragm. The relief means, preferably as amatter of practice and convenience, may also comprise a slotted openingalone and running axially along the rudder in which the width of theslot may be as much as up to about one-third of the circumference of therudder. The relief opening may also be adjustable so that varyingconditions can be accommodated by the proper setting of a cover fittingover the slot or a portion thereof. The above are features and objectsof the instant invention that may be used with Kort and Erlbacher patentrudder designs.

Other features and objects of this invention will appear in the detaileddescription which follows and will be otherwise apparent to thoseskilled in the art.

For the purpose of illustration of this invention, there are shown inthe accompanying drawings several embodiments thereof. It is to beunderstood that these drawings are for the purpose of example only,however, and that the invention is not limited thereto.

In the drawings:

FIGURE 1 is a fragmentary and side elevation of the rear of a vesselfitted with a rudder spaced aft of the propeller and having the reliefmeans of the instant invention;

FIGURE 2 is a view in section taken on the line 22 of FIGURE 1;

FIGURE 3 is a view in vertical section taken along the axis of thepropeller and the rudder of the vessel of FIG- URE 1;

FIGURE 4 is a view similar to FIGURE 3, but showing the use of a rudderfitting over the propeller as in the Kort design;

FIGURE 5 is a view taken similarly to FIGURE 4, but showing a modifieddesign;

FIGURE 6 is a view in front elevation of a slotted tubular rudder fittedwith a flexible diaphragm which provides the relief means of thisinvention and shows the action of the wheel race at normal r.p.m.;

FIGURE 7 is a view similar to FIGURE 6 showing the action of the wheelrace at an increased r.p.m.;

FIGURE 8 is a view in section showing the action of the flexiblediaphragm when the r.p.m. is decreased to provide a wheel race ofgreater diameter;

FIGURE 9 is a view in side elevation of a modified rudder having aslotted relief port;

FIGURE 10 is a view in section taken on the line 1010 of FIGURE 9;

FIGURE 11 is a view in side elevation of a further modified tubularrudder having a relief port which is adjustable with respect to itseffective size by means of a cover plate; and

FIGURE 12 is an enlarged view in section taken on line 1212 of FIGURE11.

The rudder of FIGURES 1 to 3 is generally identified by the referencenumeral 20, and, as shown therein, is pivotally attached through arudder post 22 to the hull of the vessel 24. The vessel is provided witha conventional propeller 26, and the rudder is located axially withrespect to the propeller and aft thereof. As seen in FIG- URES 2 and 3,the rudder is constructed of a shell member 28 having an axially runningslot 30 at the bottom thereof. The slot 36) provides the relief means ofthis invention and can extend in width up to about one-third thecircumference of the shell 28. By means of this particular location ofthe slot at the bottom of the shell, the draft of the vessel isdecreased besides obtaining the increased operating efliciency andpropulsive and steering effectiveness of the invention.

In FIGURE 4 a modified rudder 36 is shown which encloses the propeller26. This modification is in a form similar to the Kort design. Therudder is otherwise identical in construction with the rudder 20 ofFIGURES 1 to 3, except for the change in position.

In FIGURE 5 a further modification is shown through the use of a rudder33. This rudder is also used in a Kort design as it fits over thepropeller 26, but it may also be used aft of the propeller. In thismodification, however, the rudder 38 has a slot 40 opening at the frontof the rudder, Whereas, the rear of the rudder is entirely enclosed at42. In this modification, at the point of Patented Dec. 24, 1963greatest wheel. race effect, in, other words, at the propeller wheel andslightly to the rear thereof, the relief means is provided, whereas atthe rearward portion the rudder is of completely tubular design with norelief means provided. This design provides somewhat greater strengthwhile still combining a portion of the relief means of this invention.

In FIGURES 6 through 8 a still further modification is shown through therudder designated 46. This rudder is of the same design as rudder 20,but, in addition, has a flexible sleeve-like diaphragm 48 installed inthe interior thereof, which shows the action of the wheel race. Theflexible diaphragm provides for the capture of the, wheel race and atthe same time is distensible from the average condition shown in FIGURE6 to the higher r.p.m. conditionof FIGURE 7 through the decreased r.p.m.condition of FIGURE 8.

In FIGURES 9 and 170 a further modification of the rudder of thisinvention is generally designated by the reference numeral 503. In thismodification a relief port 52. is provided. This relief port runsaxially along the circumference of the rudder shell, but does not runall the way to either the front or the rear. By this construction a ribportion 4 at the front and a rib portion 55 at the rear are provided,which provides increased strength, It will he understood that the slotmay extend somewhat in greater length than shown in FIGURE 9 and mayalso be of greater width as previously described. Another slot may alsobe used on the opposite side where desired for balancing considerations.

A still-further modification of the rudder of this invention is shown inFIGURES 11 and 12, designated by the reference numeral 60; In thismodification a relief port 52 is employed similar to that of FIGURES 9and 10. However, an, adjustable cover plate 62 is utilized, slideablewithin tracks 64. By adjustment of the cover plate to a rearwarddirection to that shown in FIGURE 11, a, greater, portion of the reliefport will be covered to reduce the effective area. Likewise, by movingthe relief. port to the front or to the left from the position shown inFIGURE 11, a greater area of the relief port will be opened up, whichmay be desired for increased speeds and increased loads. Thus, when therelief port is partially closed, or made, of reduced effective area, therudder may be made toaccommodate atoptimum operating efficiency, loweredspeeds and loads, and a full range of operating adjustment is provided.

Operation Although it is not necessary for the understanding of thisinvention to discuss the theoretical function of the rudder with therelief means, and since it is not desired to be bound by the theory ofoperation accordingly, applicant does not wish to be limited by thedescription of the operation of the wheelrace through the tubular rudderHowever, for the purpose of explanation of the action of. the waterthrough the rudder, it can be imagined that the rudder in the shape of atube of rather large diameter for its, length is employed and is able tobe pulled through the water by some means so the water is able to passthrough the tube in line with the direction it is being pulled. In suchaction y can represent the volume of water per minute going through thetubular rudder when it is pulled at top speed and then the volume offlow at no speed, or at the stationary condition, is zero. Then thevolume of flow at speeds between zero speed and top speed would rangeproportionally between zero and y.

Now it can be considered that there be placed on the front end of thetube a propeller that is capable of pumping x gallons of water perminute through the tube. If this propeller could pull the tube throughthe water at top speed, the flow of water through the tube would be nearx-l-y gallons per minute. If the tube were held baclc but the propellerwere run at top rpm, the gallons per minute going through the tube wouldbe x+0 or x gallons per minute. Propeller speeds from O to top r.p.m.would give varying flows through the tube.

The above example is used for descriptive purposes for in actualpractice, and from work done on the tubular rudder, it has been foundthat there is, due to water action and friction within the tube, anoptimum frontal area of the tube for each volume of flow going throughit to obtain maximum performance from the propulsion system. In actualvessel operation all various conditions, as shown in the above example,may be experienced within a normal operating day. If the boat isoperated with no tow or pay load, there would be very little restrictionin the tubular rudder going through the water, which approximates acondition of little slip. If a larger tow or pay load is employed, thevessel would not move through the water as fast, although the propellermay be turning at the same r.p.m., and this corresponds to a conditionof greater slip. Around these results and Ber noullis theorem are whatthe invention is based upon.

In order to provide a tubular rudder of the Kort design, or according tothe Erlbacher patent, for eflicient operation under all load conditions,the relief means upon the rudder is provided by way of ports, openings,or slits in the sides of the rudder to act as a valve. Thus, there isprovided a relief means for the allowance of greater or lesser amountsof water to pass through the rudder giving the effect of an adjustablefrontal area under a set range of conditions. As an example of theoperation, it can be imagined that an Erlbacher patent type of rudder isdesigned for optimum operation where the boat is traveling at one-halfspeed forward under a heavy tow or pay load, but the propeller isturning at about top r.p.m. Under this condition, if the boat were thenper mitted to go at-top speed by reducing the load, the frontal area ofthe rudder would have to be decreased for top efliciency. If the forwardmotion of the boat were almost stopped by a very heavy load, the frontalarea would have to be increased. To accommodate the above conditions, asection is removed from the bottom of the rudder in the form of alengthwise slit, such as the slit or opening 30 in the rudder shell ofFIGURE 2.

For further understanding, reference is also made to FIGURES 6 7 and 8where a flexible diaphragm 48 is employed, which covers the opening 30.The diaphragm would then take the normal position at half r.p.m. andfull load as shown in FIGURE 6. At high r.p. m. with the same load theconditions would be as shown in FIG- URE 7, while at lower r.p.m. withthe same load the conditions would be as shown in FIGURE 8.

It may also be assumed that for another design for a different set ofoperating conditions FIGURE 6 represents the condition of half load andhigh rpm. Then, if the load is decreased, there will be less slippageand the condition at high r.p.m. will be as in FIGURE 7, while if theload is increased to full load still operating at high r.p.m. thecondition will be as shown in FIG- URE 8.

In actual practice, however, the rubber diaphragm may be removed as inthe rudder of FIGURES 1, 2 and 3, and the other modifications, and theoutward and inward pressure will equalize themselves to form similarflow patterns. The width of the opening may be up to about one-third ofthe circumference of the rudder shell. This width will depend somewhaton the propeller design, the r.p.m., and the tow or pay load for whichthe boat is designed and normally operated. The use of the slit orrelief opening in the shell has been explained for example anddescriptive purposes only, and the location can be at various points onthe shell or nozzle, and may be provided for by the use of holes, ports,etc., with varying degree of success. However, the use of an axial slit,as shown in FIGURE 2, is quite desirable, and where it is of substantialcircumferential width, it is desirably O positioned at the bottom of theshell to reduce the draft of the rudder.

Through the operation of the tubular rudder with relief means of theinvention, a number of advantages are obtained. Thus, the draft of theboat is not increased, and may actually be decreased, While the reliefvalve can be employed to equalize flow. Efficiency may be increasedWithin a wide range of speeds. Also, besides use in the Erlbacher patentrudder, the Kort nozzle may be adapted for variable speeds and flowconditions, and the rudder offers propeller Wheel protection.Additionally, vibration and turbulence are decreased and converselyspeed and thrust are increased and also the backing ability of the Kortnozzle is increased.

Various changes and modifications in the employment of the relief meansin the tubular rudder of this invention may be made Within the skill ofthe art. Such changes and obvious modifications are within the scope andteaching of this invention as defined by the claims appended hereto.

What is claimed is:

1. A rudder for marine vessels pivotally mounted about a vertical axisupon the hull of a vessel, said rudder comprising a hollow tube-likeshell open at the front and rear ends, said shell having an internaldiameter to receive and substantially confine the propeller race of apropeller of the vessel, and adjustable relief means on said shell topermit passage of propeller races of increased diameter through saidshell.

2. A rudder for marine vessels pivotally mounted about a vertical axisupon the hull of a vessel, said rudder comprising a hollow tube-likeshell open at the front and rear ends, said shell having an internaldiameter to receive and substantially confine the propeller race of apropeller of the vessel, and adjustable relief means on said shell topermit passage of propeller races of increased diameter through saidshell, said relief means constituting an elongated section of the shellpassing a propeller race of increased diameter.

3. A rudder for marine vessels pivotally mounted about a vertical axisupon the hull of a vessel, said rudder comprising a hollow tube-likeshell open at the front and rear ends, said shell having an internaldiameter to receive the propeller race of a propeller of the vessel, andrelief means on said shell to permit passage of propeller races ofincreased diameter through said shell, said relief means constituting anelongated section of the shell of expansible diameter.

4. A rudder for marine vessels pivotally mounted about a vertical axisupon the hull of a vessel, said rudder comprising a hollow tube-likeshell open at the front and rear ends, said shell having an internaldiameter to receive the propeller race of a propeller of the vessel, andrelief means on said shell to permit passage of propeller races ofincreased diameter through said shell, said relief means constituting anelongated section of expansible diameter, said elongated section beingflexible and the remainder of said shell being rigid.

5. A rudder for marine vessels pivotally mounted about a vertical axisupon the hull of a vessel, said rudder comprising a hollow tube-likeshell open at the front and rear ends, said shell having an internaldiameter to receive and substantially confine the propeller race of apropeller of the vessel, and adjustable relief means on said shell topermit passage of propeller races of increased diameter through saidshell, said relief means comprising an elongated slot in the shellrunning coaxially therewith.

6. A rudder for marine vessels pivotally mounted about a vertical axisupon the hull of a vessel, said rudder comprising a hollow tube-likeshell open at the front and rear ends, said shell having an internaldiameter to receive and substantially confine the propeller race of apropeller of the vessel, and adjustable relief means on said shell topermit passage of propeller races of increased diameter through saidshell, said relief means being adjustable in size by an adjustable coverplate movable into and out of covering relationship with said slot.

7. A rudder for marine vessels pivotally mounted about a vertical axisupon the hull of a vessel, said rudder comprising a hollow tube-likeshell open at the front and rear ends, said shell having an internaldiameter to receive and substantially confine the propeller race of apropeller of the vessel, and adjustable relief means on said shell topermit passage of propeller races of increased diameter through saidshell, said relief means comprising an elongated slot in the shellextending from the front to the rear.

8. A rudder for marine Vessels pivotally mounted about a vertical axisupon the hull of a vessel, said rudder comprising a hollow tube-likeshell open at the front and rear ends, said shell having an internaldiameter to receive and substantially confine the propeller race of apropeller of the vessel, and adjustable relief means on said shell topermit passage of propeller races of increased diameter through saidshell, said relief means comprising an elongated slot in the shellrunning coaxially therewith, said slot having a width up to aboutone-third the circumference of said shell.

9. In combination with a marine vessel having a bladed propeller, arudder pivotally mounted about a vertical axis upon the hull of a vesselcomprising a hollow tubelike shell open at the front and rear ends andfitting around said propeller in coaxial relationship, said shell havingan internal diameter slightly larger than the propeller to receive andsubstantially confine the propeller race, and adjustable relief means onsaid shell to permit the passage of propeller races of increaseddiameter through said shell.

10. In combination with a marine vessel having a bladed propeller, arudder pivotally mounted about a vertical axis upon the hull of a vesselcomprising a hollow tubelike shell open at the front and rear ends andfitting around said propeller in coaxial relationship, said shell havingan internal diameter slightly larger than the propeller to receive thepropeller race, and relief means on said shell to permit the passage ofpropeller races of increased diameter through said shell, said reliefmeans constituting an enlongated section of expansible diameter, saidelongated section being fiexible and the remainder of said shell beingrigid.

11. In combination with a marine vessel having a bladed propeller, arudder pivotally mounted about a vertical axis upon the hull of a vesselcomprising a hollow tubelike shell open at the front and rear ends andfitting around said propeller in coaxial relationship, said shell havingan internal diameter slightly larger than the propeller to receive andsubstantially confine the propeller race, and adjustable relief means onsaid shell to permit the passage of propeller races of increaseddiameter through said shell, and said relief means comprising anelongated slot in the shell running coaxially therewith.

12. In combination with a marine vessel having a bladed propeller, arudder pivotally mounted about a vertical axis upon the hull of a vesselcomprising a hollow tubelike shell open at the front end and rear endsand spaced axially with respect to said propeller, said shell having aninternal diameter slightly larger than the propeller to receive andsubstantially confine the propeller race, and adjustable relief means onsaid shell to permit the passage of propeller races of increaseddiameter through said shell.

13. In combination with a marine vessel having a bladed propeller, arudder pivotally mounted about a vertical axis upon the hull of a vesselcomprising a hollow tubelike shell open at the front end and rear endsand spaced axially with respect to said propeller, said shell having aninternal diameter slightly larger than the propeller to receive thepropeller race, and relief means on said shell to permit the passage ofpropeller races of increased diameter through said shell, said reliefmeans constituting an elongated section of expansible diameter, saidelon- 8 gated section being flexible and the remainder of said ofpropeller races of increased diameter through said shell being rigid.shell, said relief means comprising an elongated slot in 14. Incombination with a marine vesselhav ing a bladed the shell runningcoaxially therewith. propeller, a rudder pivotally mounted about avertical axis upon the hull of a vessel comprising a hollow tube- 5References Cited In the file 0f ihlstpatellt like shell open at thefront end; and rear ends and spaced UNITED S A PATENTS axially withrespect to said propeller, saidshellhaving an internal diameter slightlylarger than the propeller to re- 2322 cave and substantially confine thepropeller race, and 904,313 Davis Nov. 17, 1908 adjustable relief meanson saidshell to permit the passage. 10

1. A RUDDER FOR MARINE VESSELS PIVOTALLY MOUNTED ABOUT A VERTICAL AXISUPON THE HULL OF A VESSEL, SAID RUDDER COMPRISING A HOLLOW TUBE-LIKESHELL OPEN AT THE FRONT AND REAR ENDS, SAID SHELL HAVING AN INTERNALDIAMETER TO RECEIVE AND SUBSTANTIALLY CONFINE THE PROPELLER RACE OF APROPELLER OF THE VESSEL, AND ADJUSTABLE RELIEF MEANS ON SAID SHELL TOPERMIT PASSAGE OF PROPELLER RACES OF INCREASED DIAMETER THROUGH SAIDSHELL.